Document and Entity Information - shares
9 Months Ended
Sep. 30, 2019
Nov. 08, 2019
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Document Quarterly Report true  
Document Transition Report false  
Security Exchange Name NASDAQ  
Trading Symbol LIFE  
Entity Registrant Name aTYR PHARMA INC  
Entity Central Index Key 0001339970  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Current Fiscal Year End Date --12-31  
Entity Filer Category Non-accelerated Filer  
Entity Shell Company false  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period true  
Entity Common Stock, Shares Outstanding   3,890,185
Entity File Number 001-37378  
Entity Tax Identification Number 20-3435077  
Entity Address, Address Line One 3545 John Hopkins Court  
Entity Address, Address Line Two Suite #250  
Entity Address, City or Town San Diego  
Entity Address, State or Province CA  
Entity Incorporation, State or Country Code DE  
Entity Address, Postal Zip Code 92121  
City Area Code 858  
Local Phone Number 731-8389  
Title of 12(b) Security Common Stock, par value $0.001 per share